From: Sebastian Andrzej Siewior bigeasy@linutronix.de
[ Upstream commit 9848417926353daa59d2b05eb26e185063dbac6e ]
The intel powerclamp driver will setup a per-CPU worker with RT priority. The worker will then invoke play_idle() in which it remains in the idle poll loop until it is stopped by the timer it started earlier.
That timer needs to expire in hard interrupt context on PREEMPT_RT. Otherwise the timer will expire in ksoftirqd as a SOFT timer but that task won't be scheduled on the CPU because its priority is lower than the priority of the worker which is in the idle loop.
Always expire the idle timer in hard interrupt context.
Reported-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Sebastian Andrzej Siewior bigeasy@linutronix.de Signed-off-by: Thomas Gleixner tglx@linutronix.de Link: https://lore.kernel.org/r/20210906113034.jgfxrjdvxnjqgtmc@linutronix.de Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/idle.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index 912b47aa99d8..d17b0a5ce6ac 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -379,10 +379,10 @@ void play_idle_precise(u64 duration_ns, u64 latency_ns) cpuidle_use_deepest_state(latency_ns);
it.done = 0; - hrtimer_init_on_stack(&it.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + hrtimer_init_on_stack(&it.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD); it.timer.function = idle_inject_timer_fn; hrtimer_start(&it.timer, ns_to_ktime(duration_ns), - HRTIMER_MODE_REL_PINNED); + HRTIMER_MODE_REL_PINNED_HARD);
while (!READ_ONCE(it.done)) do_idle();